[DAG] add helper to bind memop chains; NFCI

This step is just intended to reduce code duplication rather than change any functionality.

A follow-up would be to replace PPCTargetLowering::spliceIntoChain() usage with this new helper.

Differential Revision: https://reviews.llvm.org/D33649

llvm-svn: 305192

1 files changed, 18 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index dff8bd2ad37..7abdc76cb00 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -7244,6 +7244,24 @@ void SelectionDAG::TransferDbgValues(SDValue From, SDValue To) {
     AddDbgValue(I, ToNode, false);
 }
 
+void SelectionDAG::makeEquivalentMemoryOrdering(LoadSDNode *OldLoad,
+                                                SDValue NewMemOp) {
+  assert(isa<MemSDNode>(NewMemOp.getNode()) && "Expected a memop node");
+  if (!OldLoad->hasAnyUseOfValue(1))
+    return;
+
+  // The new memory operation must have the same position as the old load in
+  // terms of memory dependency. Create a TokenFactor for the old load and new
+  // memory operation and update uses of the old load's output chain to use that
+  // TokenFactor.
+  SDValue OldChain = SDValue(OldLoad, 1);
+  SDValue NewChain = SDValue(NewMemOp.getNode(), 1);
+  SDValue TokenFactor =
+      getNode(ISD::TokenFactor, SDLoc(OldLoad), MVT::Other, OldChain, NewChain);
+  ReplaceAllUsesOfValueWith(OldChain, TokenFactor);
+  UpdateNodeOperands(TokenFactor.getNode(), OldChain, NewChain);
+}
+
 //===----------------------------------------------------------------------===//
 //                              SDNode Class
 //===----------------------------------------------------------------------===//